[tf.data] Experimental transformations for windowing and batching of windows.

This change introduces the `window` tf.data transformation, which can be used to create windows of elements (represented as a dataset) from a dataset. This transformation enables applying different batching logic to different components of a dataset.

To illustrate the benefits of the transformation, this CL also introduces transformations for batching and padded batching of windows of both dense and sparse tensors. Notably, padded batching of sparse tensors was previously not possible.

PiperOrigin-RevId: 203179522